Abstract
AbstractIn Central Europe, massive losses in species richness of breeding birds have been documented in the last decades, but the question arises whether species richness is currently still decreasing or again increasing due to conservation efforts. In this study, we investigated regional and local species richness as well as mean number of breeding pairs and mean biomass per tetrad over a period of some 20 years at Lake Constance. Three quantitative censuses of 303 tetrads (2 × 2 km2) repeated at 10-year intervals (1980–1981, 1990–1992, 2000–2002) revealed an increase in regional species richness (total number of breeding species). At the same time, however, a strong decline in local species richness (number of breeding species per tetrad), number of breeding pairs, and estimated biomass were observed. Changes of species richness differed markedly between Nonpasserine and Passerine birds. Whereas species richness of Nonpasserines remained constant from 1980 to 1990, and even increased between 1990 and 2000, that of Passerines decreased in both periods. This indicates that effects of conservation efforts apparently eclipse more general effects of climate and habitat change in Nonpasserines. The massive abundance and biomass losses observed in formerly common Passerine species are not compensated by gains in populations of Nonpasserine species. The results of the three bird censuses at Lake Constance imply that ongoing habitat degradation and human impacts as well as increasing effects of climate change are the main drivers of the observed population changes.
Highlights
In order to be able to halt biodiversity loss by 2010, conservationists ‘‘must first identify which species or species groups are in decline’’ (Sanderson et al 2006)
At Lake Constance, avian species richness increased on a regional scale from 141 (1980) and 146 (1990) to 154 (2000) breeding species
We found an increase in regional species richness in Nonpasserines, whereas in Passerines regional species richness remained almost constant
Summary
In order to be able to halt biodiversity loss by 2010, conservationists ‘‘must first identify which species or species groups are in decline’’ (Sanderson et al 2006). In Europe, avian diversity in agricultural landscapes has declined markedly during the last decades as documented in numerous studies and reviews (e.g., Bohning-Gaese and Bauer 1996; Pain and Pienkowski 1997; BirdLife International 2004; Gregory et al 2004; Newton 2004; Bauer et al 2005a, b; PECBM 2006). To habitat degradation and fragmentation, reductions of biodiversity have increasingly been attributed to climate change (e.g., Walther et al 2002; Julliard et al 2003; Travis 2003). These effects, in addition to human interference (e.g., hunting), are thought to be responsible. J Ornithol (2008) 149:217–222 for the recent massive declines observed in Afro-Palearctic long-distance migrants (Bohning-Gaese and Bauer 1996; Berthold 2001; BirdLife International 2004; Sanderson et al 2006). Transportation has led to introductions and range expansions of a considerable number of exotic species into Europe (McKinney and Lockwood 1999)
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